In the field of internal combustion engines, it is known that turbulence may improve the preparation of the air-fuel mixture in the combustion chamber and the combustion thereon, to thereby improving the performance of the engine. Conventional air induction system generally provides each combustion chamber of the engine with at least a straight inlet port, which is formed for minimizing the resistance to the intake airflow, and thereby increasing the volumetric efficiency.
When the engine is operating at high load, although the flow resistance of the inlet port is low, sufficient turbulence is caused in the combustion chamber for keeping the air-fuel mixing and combustion at acceptable level. On the contrary, when the engine is operating at low and medium load, the low flow resistance of the inlet port and the low velocity of the intake airflow are not generally sufficient to generate adequate turbulence in the combustion chamber.
In order to improve turbulence, have been proposed air induction systems which provide each combustion chamber of the engine not only with a straight inlet port, but also with a further swirl inlet port specifically designed for imparting swirling motion to the intake airflow. A swirl inlet port of this kind is the so called helical port, which extends helically around the axis of the intake valve seating surface. Such air induction systems further comprises a swirl controlling element for each combustion chamber of the engine, typically in form of a rotating flap.
This swirl controlling flap is located in a passageway connecting the intake manifold to the straight inlet port of the combustion chamber, for selectively close said passageway in accordance with engine load conditions. When the engine is operating at low or medium load, the swirl controlling flap is kept in closed position for preventing the intake air to flow through the straight inlet port. Therefore, the major portion of the intake air flows into the combustion chamber through the swirl inlet port, achieving a strong turbulence.
When the engine is operating at high load, the swirl controlling flap is kept in open position for allowing intake air to flow into the cylinder through the straight port. The major portion of the intake air flows into the combustion chamber through the straight inlet port, due to the less flow resistance of the latter relative to the swirl inlet port, to thereby reducing pressure drop and achieving a high volumetric efficiency.
All swirl controlling flaps are simultaneously rotate between their open and closed position by means of a common electromechanical actuator. The electromechanical actuator generally comprises a movable shaft which is called actuator shaft. The electromechanical actuator can be of the rotational or linear kind, such that the actuator shaft is a rotating shaft or a reciprocating shaft respectively.
The actuator shaft is mechanically coupled with the swirl controlling flaps by means of a proper cinematic chain, which shall comprise gears or levers. The cinematic chain is provided for transforming any rotation or linear movement of the actuator shaft to a correspondent rotation of the swirl controlling flaps.
The electromechanical actuator further comprises an embedded position sensor for real time sensing the angular or linear position of the actuator shaft. The electromechanical actuator is controlled by an engine control unit, on the base of the signal from the position sensor and the engine operating condition.
Alternatively, the electromechanical actuator can be provided with an embedded microprocessor based controlled, which control the rotations of the actuator shaft on the base of the signal from the position sensor, and which is connected to the engine control unit, for receiving from the latter instructions about the positions to reach in response of engine operating conditions. As a matter of fact, the engine control unit detects the position of the actuator shaft and the operating condition of the engine, and when the engine is operating at low or medium load, commands the electromechanical actuator to rotate the swirl controlling flaps in closed position, and when the engine is operated at high load, commands the electromechanical actuator to rotate the swirl controlling flaps in open position. Therefore, during normal operation, the actuator shaft is commanded for moving in both directions between a first and a second final position, which respectively correspond to open and closed position of the swirl controlling flaps.
At least one aim is to detect the integrity of the cinematic chain connecting the actuator movable shaft to the swirl controlling valves. Another aim of the present invention is to meet the goal with a rather simple, rational and inexpensive solution. In addition, other aims, desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.